Moringa (Moringa oleifera) leaf extracts inhibit spore germination of Alternaria solani, causal agent of early blight disease of tomato (Solanum lycopersicum)

Abstract

Alternaria solani is highly infective and can sporulate on tomato at 13.2 × 106 spores mL−1. The fungicidal effect of Moringa oleifera leaf chloroform and aqueous extracts (MLCE and MLAE, respectively) was investigated in vitro to determine the inhibitory effect on germination of spores (conidia) of A. solani. Mixtures of spore suspension and MLCE, as well as MLAE (1:1), were prepared and dropped on slides by micropipette with 20 µL spore suspension of A. solani and 20 µL of MLCE and MLAE. The two treatments, MLCE and MLAE, were applied at four concentrations (62.5, 125, 250 and 500 mg mL−1) and compared with negative (distilled water; no extracts) and positive (diflucan, a commercial fungicide) controls with five replicates. The two extracts showed relatively high inhibitory effects on the germination of conidia from the lowest to the highest concentration. Germination of conidia decreased with increase in the concentrations of the extracts. The study showed that 250 mg mL−1 is the optimum concentration for both MLCE and MLAE. The highest concentration inhibited germination (0.0%) in both extracts. Based on the results from the present study, MLCE and MLAE are both effective in inhibiting germination of A. solani conidia.